There is a need for more effective therapies to reduce morbidity and mortality from cardiovascular disease. Inflammation plays a central role in the pathogenesis of atherosclerosis but no randomized studies have evaluated anti-inflammatory therapy in patients with acute coronary or cerebrovascular disease. We performed a pilot randomized controlled trial comparing the effect of colchicine 1 mg per day with placebo on high sensitivity C-reactive protein (CRP) levels and platelet function in 80 patients with acute coronary syndrome or acute ischemic stroke who were followed for 30 days. Clinical status was ascertained for 74 (92.5%) patients and CRP levels were obtained in 68 (85%) of patients at follow up. Colchicine did not significantly reduce absolute hs-CRP at 30 days [median 1.0 mg/l (range 0.2, 162.0) versus 1.5 mg/l (0.2, 19.8), P = 0.22] or difference in CRP from baseline to 30 days [absolute difference 7.0 mg/l (-61.0, 87.8) vs. 7.1 mg/l (-1.0, 144), P = 0.64]. The proportion of patients with CRP <2 mg/l at follow up did not differ according to treatment allocation (77% vs. 62%, X (2) 1.84, P = 0.18). There was also no difference in platelet function assessed using platelet aggregation with ADP (5 μmol), arachidonic acid (0.5 mmol), collagen (1 μg/ml) and collagen (5 μg/ml) (P = 0.86, P = 0.64, P = 0.76, P = 0.20, respectively), and urine dehydrothromboxane B2 (P = 0.54). Colchicine was associated with an excess of diarrhoea (X(2) 4.14, P = 0.04). In conclusion, our pilot study provided no evidence that colchicine 1 mg daily for 30 days compared with placebo suppresses inflammation in patients with acute coronary syndrome or acute ischemic stroke.